This application claims priority of Japanese Patent Application No. 2000-223029, filed Jul. 24, 2000.
1. Field of the Invention
The present invention relates to an electrostatic adsorption apparatus for electrostatically adsorbing a plastic film, and a method of electrostatically adsorbing plastic film using this apparatus.
The present application is based on a patent filed in Japan (Japanese Patent Application No. 2000-223029), and the described contents of that Japanese application are contained in a portion of the present specification.
2. Description of the Related Art
It is necessary to fix the plastic films comprised of metal, organic compounds or inorganic compounds and so forth on a sample stand. In cases in which these plastic films are subjected to surface processing and treatment such as heat treatment or plasma treatment, or are adhered or joined with other materials.
Consequently, known methods of the prior art for fixing plastic films on a sample stand include the following:
(1) Methods in which the plastic film is adhered using an adhesive and so forth;
(2) Methods in which the periphery of the plastic film is mechanically fixed using screws, clips, adhesive tape and so forth;
(3) Methods in which the plastic film is fixed by vacuum suction; and,
(4) Methods in which the plastic film is electrostatically adsorbed using electrostatic force.
However, each of the above methods for fixing a plastic film to a sample stand of the prior art has their respective problems.
Namely, in the case of the methods described in (1) above, since it is necessary to uniformly apply adhesive to the plastic film and remove the adhesive following surface treatment, the work was tedious. In addition, since the plastic film easily trap atmospheric gas during adhesion of the plastic film, there was the problem of wrinkles forming in the plastic film.
In addition, since the plastic film expands and deforms due to heat treatment and plasma treatment during surface treatment, there was the problem of the plastic film becoming deformed and separating from a sample stand due to the difference in thermal expansion between the sample stand and plastic film.
Moreover, since the adhesive evaporates when surface treatment is performed in a vacuum, there was the problem of these methods being unable to be used in a vacuum.
In the case of the methods described in (2) above, there was the problem of being unable to process the fixed portion of the plastic film. In addition, there was the problem of wrinkles forming easily in the plastic film due to local differences in tension during fixation. Moreover, the plastic film expanded and deformed due to heat treatment and plasma treatment performed during surface treatment. When the plastic film expands and deforms, there was the problem of the portion of the plastic film not fixed to the sample stand lifting from the sample stand due to the difference in thermal expansion between the sample stand and plastic film.
In the case of the methods described in (3) and (4) above as well, there were the problems of wrinkle formation, deformation and separation in the plastic film. These problems occur due to expansion and deformation of the plastic film caused by heat treatment and plasma treatment during surface treatment and the difference in thermal expansion between the sample stand and plastic film.
In consideration of the above circumstances, the object of the present invention is to provide a plastic film electrostatic adsorption apparatus and an electrostatic adsorption method. That eliminates the need for tedious procedures such as coating and removal of adhesive while also enabling surface treatment to be performed even in a vacuum.
More specifically, the object of the present invention is to provide a plastic film electrostatic adsorption apparatus and electrostatic adsorption method for electrostatically adsorbing a plastic film. That eliminates the occurrence of wrinkling, deformation and separation of the plastic film caused by differences in thermal expansion between the sample stand and plastic film even if the plastic film expands and deforms due to heat treatment or plasma treatment performed during surface treatment of the plastic film.
The plastic film electrostatic adsorption apparatus of the present invention is a plastic film electrostatic adsorption apparatus comprising an electrostatic adsorption electrode, an insulated dielectric layer that covers the above electrostatic adsorption electrode and has a center line average roughness of the adsorption surface on which the plastic film is placed of 0.5 xcexcm or less, and a power supply electrode that applies a voltage to the above electrostatic adsorption electrode.
According to this plastic film electrostatic adsorption apparatus, surface treatment can be performed even in a vacuum without requiring tedious procedures such as application and removal of an adhesive. In addition, there is no occurrence of wrinkling, deformation or separation of the plastic film caused by differences in thermal expansion between the electrostatic adsorption surface of the electrostatic adsorption electrode and plastic film. Even if the plastic film expands and deforms due to heat treatment or plasma treatment during surface treatment.
In addition, the above electrostatic adsorption electrode of the plastic film electrostatic adsorption apparatus of the present invention employs a bipolar structure having a positive electrode and negative electrode, and is characterized by its outermost end being homopolar.
According to this plastic film electrostatic adsorption apparatus, the plastic film can be electrostatically adsorbed even in a state in which plasma is not generated. In addition, this plastic film electrostatic adsorption apparatus eliminates the need for tedious procedures such as coating and removal of adhesive. In addition, uniform etching can be performed on the plastic film.
In addition, the interval between the positive electrode and negative electrode that compose the above electrostatic adsorption electrode of the plastic film electrostatic adsorption apparatus of the present invention is characterized as being 1 to 10 times the thickness of the above insulated dielectric layer.
According to this plastic film electrostatic adsorption apparatus, the electrostatic adsorption force that adsorbs the plastic film is partially weakened, thereby making it easier to evacuate atmospheric gas entrapped between the plastic film and electrostatic adsorption electrode and preventing the formation of wrinkles in the plastic film.
In addition, the volumetric resistivity value of the above insulated dielectric layer of the plastic film electrostatic adsorption apparatus of the present invention is characterized as being from 108 to 1012 xcexa9cm.
According to this plastic film electrostatic adsorption apparatus, there is no generation of leakage current during electrostatic adsorption of the plastic film. In addition, there is no wrinkling or deformation even when the plastic film expands and deforms due to heat treatment or plasma treatment performed during surface treatment.
In addition, the plastic film electrostatic adsorption method of the present invention is characterized by the surface area of adsorption side of the electrostatic adsorption electrode being 10 to 80% of the surface area on which the plastic film is in contact with the adsorption surface of the electrostatic adsorption electrode when using the above plastic film electrostatic adsorption apparatus.
According to this plastic film electrostatic adsorption method, even if atmospheric gas is entrapped between the electrostatic adsorption electrode and plastic film during electrostatic adsorption of the plastic film, since the entrapped atmospheric gas is easily evacuated, there is no wrinkling or deformation of the plastic film.
In addition, in the plastic film electrostatic adsorption method of the present invention, a plastic film is electrostatically adsorbed onto an adsorption surface of an insulated dielectric layer using the above plastic film electrostatic adsorption apparatus in a state in which the outermost end of the electrostatic adsorption electrode protrudes beyond the outermost edge of the plastic film, and the length of its protrusion is 4 mm or less.
According to this plastic film electrostatic adsorption method, the outer periphery of the plastic film does not lift from the electrostatic adsorption electrode. In addition, there is no roughening of the electrostatically adsorbed surface due to electrical charge concentrating on the electrostatically adsorbed surface of the plastic film on the electrostatic adsorption electrode and increased collision of charged active species during etching treatment and so forth.
In addition, in the plastic film electrostatic adsorption method of the present invention, the electrostatic adsorption voltage is either lowered or the application of electrostatic adsorption voltage is discontinued after electrostatic adsorption of the plastic film using the above plastic film electrostatic adsorption apparatus.
According to this plastic film electrostatic adsorption method, the plastic film slides easily in the horizontal direction on the electrostatic adsorption electrode. Thus, even if atmospheric gas is entrapped between the electrostatic adsorption electrode and plastic film during electrostatic adsorption of the plastic film, if the application of electrostatic adsorption voltage is discontinued, the entrapped atmospheric gas is evacuated easily, thereby preventing wrinkling and deformation of the plastic film.